The semiconductor integrated circuit (IC) industry has experienced rapid growth. Technological advances in IC design and material have produced generations of ICs where each generation has smaller and more complex circuits than previous generations. In the course of IC evolution, functional density (i.e., the number of interconnected devices per chip area) has generally increased while geometry size (i.e., the smallest component (or line) that can be created using a fabrication process) has decreased.
Transistors are circuit components or elements that are often formed as a part of semiconductor fabrication. A field effect transistor (FET) is one type of transistor. Typically, a transistor includes a gate stack formed between source and drain regions. The source and drain regions may include a doped region of a substrate and may exhibit a doping profile suitable for a particular application. The gate stack is positioned over the channel region and may include a gate dielectric interposed between a gate electrode and the channel region in the substrate. FETs can be used as negative capacitance devices. However, existing negative-capacitance FETs may still have shortcomings, such as shortcomings with respect to reliability.
Therefore, although existing negative-capacitance FETs have been generally adequate for their intended purposes, they have not been entirely satisfactory in every aspect. For an example, negative-capacitance FETs with improved reliability are desired.